Printer

ABSTRACT

A printer performs printing on a thermal paper drawn from roll sheets having different widths. The printer has a thermal head and a platen roller arranged opposite to the thermal head and mounted to undergo rotation for sending out the thermal paper in a state of sandwiching the thermal paper between the thermal head and the platen roller. Elastic members are arrayed along the width direction of the thermal paper and are provided on an opposite side of the platen roller with respect to the thermal head for pressing the thermal head toward the platen roller. Only one of the elastic members is provided with a pressing force releasing mechanism for separating the one elastic member from the thermal head according to a width of the one roll sheet from which the thermal paper is drawn and for releasing pressing of the thermal head by the one elastic member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a printer for performing printing ofvarious types of information on a thermal paper drawn from a roll sheet.

2. Description of the Related Art

A large number of thermal printers of various types are presentlyprovided in which printing is performed by pressing a thermal headagainst a special thermal paper (heat sensitive sheet) which undergoes acolor change when heat is applied thereto. In particular, the thermalprinter is suitably used in printing a variety of labels, receipts, andtickets because it is possible to perform the printing of smooth lettersand various graphics without using toners, inks, or the like.

The above-mentioned thermal printer performs printing by sandwiching athermal paper between a platen roller and a thermal head, and by heatinga printing surface (heat sensitive surface) of the thermal paper byheating elements of the thermal head while feeding the thermal paperthrough rotation of the platen roller, thereby causing a colordevelopment of the printing surface. The thermal paper used in thethermal printer is a roll sheet type thermal paper in many cases, whichis rolled in a roll shape. Roll sheets of several types each having adifferent width (for example, 3-inch width, 4-inch width, and so on) areprovided, and used while appropriately selected according to theapplication.

Moreover, for the above-mentioned thermal printer, there is a demand fora single thermal printer that selectively performs printing on rollsheets each having a different width according to the printing purposesand applications.

However, in a conventional configuration, in a case of using a rollsheet having a smaller width (hereinafter, referred to as second rollsheet) than that of a roll sheet having a maximum usable width(hereinafter, referred to as first roll sheet), between the thermal headand the platen roller, on a widthwise outer side of the second rollsheet, a contact region is present in which the thermal paper does notpass through and the thermal head and the platen roller are brought intodirect contact with each other. In the contact region, abrasion betweenthe thermal head and the platen roller may cause a reduction of afeeding force due to a worn surface of the platen roller, damage of aprotective film on the surface of the thermal head, and the like.

In this context, it is conceivable that platen rollers respectivelycorresponding to the widths of the roll sheets are prepared, and onlythe sizes of the platen rollers are changed according to size changes ofthe roll sheets. However, this configuration leads to a problem of anincrease in cost of the apparatus.

Accordingly, for example, there is known the following configurationdescribed in JP 2007-168350 A. Specifically, an application point of aresultant force of pressing forces, which are imparted to the thermalpaper (platen roller) by the head springs supporting the thermal head,is set between a first center being a widthwise center of the first rollsheet, and a second center being a widthwise center of the second rollsheet.

However, the above-mentioned configuration of JP 2007-168350 A has aproblem that, in a case of using the second roll sheet, the pressingforce imparted to the contact region between the thermal head and theplaten roller cannot be reduced yet fully.

SUMMARY OF THE INVENTION

Therefore, the present invention has been made in view of suchcircumstances, and provides a printer capable of handling a plurality ofroll sheets each having a different width in the same apparatus whileactively reducing the pressing force to be imparted to the region inwhich the thermal head and the platen roller are brought into directcontact with each other.

In order to solve the above-mentioned problem, the present inventionprovides the following measures.

According to an exemplary embodiment of the present invention, there isprovided a printer for performing printing on a plurality of kinds ofroll sheets each having a different width, including: a thermal headincluding a large number of heating elements and being arranged along awidth direction of a thermal paper to be drawn from one of the pluralityof kinds of roll sheets; a platen roller arranged opposite to thethermal head, for sending out the thermal paper by rotating in a stateof sandwiching the thermal paper between the thermal head and the platenroller; and an elastic member provided on an opposite side of the platenroller with respect to the thermal head, for pressing the thermal headtoward the platen roller, in which the elastic member includes aplurality of elastic members arrayed along the width direction, and inwhich, of the plurality of elastic members, at least one elastic memberis provided with a pressing force releasing mechanism for separating theat least one elastic member from the thermal head according to a widthof the one of the plurality of kinds of roll sheets to be fed, and forreleasing pressing of the thermal head by the at least one elasticmember.

With this configuration, in a case of using a roll sheet having asmaller width (hereinafter, referred to as second roll sheet) than thatof a roll sheet having a maximum width (hereinafter, referred to asfirst roll sheet), it is possible to release a pressing force actingfrom the at least one elastic member to the head support member. Withthis, between the thermal head and the platen roller, it is possible toreduce the pressing force acting to a region in which the second rollsheet is not present (contact region in which the thermal head and theplaten roller are brought into direct contact with each other). Thus, itis possible to actively reduce contact pressure (platen pressure)between the thermal head and the platen roller in the contact region,and hence friction load between the thermal head and the platen rollercan be reduced. Therefore, while reducing damage caused by abrasionbetween the thermal head and the platen roller, it is possible to handlethe plurality of kinds of roll sheets each having a different width inthe same apparatus.

In addition, when compared to a conventional case in which a pluralityof kinds of platen rollers are separately prepared according to thewidths of the roll sheets, it is also possible to reduce cost of theapparatus.

Further, in the printer according to the exemplary embodiment of thepresent invention, the pressing force releasing mechanism includes alever member for moving the at least one elastic member and enabling theat least one elastic member to be brought into contact with andseparated from the thermal head.

With this configuration, through moving the at least one elastic memberand enabling the at least one elastic member to be brought into contactwith and separated from the thermal head by operation of the levermember, a user himself/herself can easily perform an operation ofreleasing the pressing force, which can improve usability.

Further, in the printer according to the exemplary embodiment of thepresent invention, the pressing force releasing mechanism includes apositioning portion for keeping the at least one elastic member at acontact position at which the at least one elastic member is broughtinto contact with the thermal head, and at a separated position at whichthe at least one elastic member is separated from the thermal head.

With this configuration, it is possible to position the at least oneelastic member at the contact position and the separated position, andhence it is possible to improve reliability of the apparatus.

Meanwhile, according to another exemplary embodiment of the presentinvention, there is provided a printer for performing printing on aplurality of kinds of roll sheets each having a different width,including: a thermal head including a large number of heating elementsand being arranged along a width direction of a thermal paper drawn fromone of the plurality of kinds of roll sheets; a platen roller arrangedopposite to the thermal head, for sending out the thermal paper byrotating in a state of sandwiching the thermal paper between the thermalhead and the platen roller; and an elastic member provided on anopposite side of the platen roller with respect to the thermal head, forpressing the thermal head toward the platen roller, in which the elasticmember includes a plurality of elastic members arrayed along the widthdirection, and in which, of the plurality of elastic members, at leastone elastic member is provided with a pressing force releasing mechanismfor moving the at least one elastic member so as to increase a stroke ofthe at least one elastic member according to a width of the one of theplurality of kinds of roll sheets to be fed, and for reducing pressingof the thermal head by the at least one elastic member.

Further, in the printer according to the another exemplary embodiment ofthe present invention, the pressing force releasing mechanism includes alever member for moving the at least one elastic member so as to reducea pressing force acting on the thermal head.

Further, in the printer according to the another exemplary embodiment ofthe present invention, the pressing force releasing mechanism includes apositioning portion for keeping the at least one elastic member at apressing force imparting position at which the at least one elasticmember generates an elastic force biasing the thermal head, and at apressing force releasing position at which the elastic force is reducedby increasing the stroke of the at least one elastic member.

With the printer according to the present invention, it is possible tohandle the plurality of kinds of roll sheets each having a differentwidth in the same apparatus while actively reducing the pressing forceto be imparted to the region in which the thermal head and the platenroller are brought into direct contact with each other.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a perspective view illustrating a state in which a paper coverof a thermal printer according to an embodiment of the present inventionis at a closed position;

FIG. 2 is a perspective view illustrating a state in which the papercover of the thermal printer according to the embodiment of the presentinvention is at an open position;

FIG. 3 is a perspective view of a printing module;

FIG. 4 is a sectional view taken along the line A-A of FIG. 3;

FIG. 5 is an explanatory diagram illustrating a switching operation froma first roll sheet mode to a second roll sheet mode, and is a sectionalview corresponding to FIG. 4;

FIG. 6 is an explanatory diagram illustrating the switching operationfrom the first roll sheet mode to the second roll sheet mode, and is aplan view of a casing;

FIG. 7 is a perspective view illustrating a printing module of a thermalprinter according to another embodiment of the present invention;

FIG. 8 is a sectional view taken along the line B-B of FIG. 7; and

FIG. 9 is an explanatory diagram illustrating a switching operation froma first roll sheet mode to a second roll sheet mode, and is a sectionalview corresponding to FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Thermal Printer

Next, embodiments of the present invention are described with referenceto the drawings. FIG. 1 is a perspective view illustrating a state inwhich a paper cover of a thermal printer is at a closed position, andFIG. 2 is a perspective view illustrating a state in which the papercover is at an open position. Note that, in the following description,for easy understanding of the invention, illustrations are simplified,as appropriate, by omitting a part of a component, simplifying a shape,changing a contraction scale, etc. Further, in the drawings, FR, LH, andUP represent a front side, a left side, and an upper side of theprinter, respectively.

As illustrated in FIGS. 1 and 2, a thermal printer (printer) 1 isconfigured to be capable of performing printing on a plurality of kindsof thermal papers P1 each having a different width. The thermal paper P1is a heat sensitive sheet which undergoes a color change when heat isapplied thereto, and the thermal paper P1 is used suitably for printinga variety of labels, receipts, and tickets. The thermal paper P1 is setin the thermal printer 1 in a state of a roll sheet P which is obtainedby rolling the thermal paper P1 so as to have a hollow hole 5, andprinting is performed on a part drawn from the roll sheet P. Note that,in the following, first, description is made of a set state of the rollsheet P having a maximum width (for example, 4-inch width) settable inthe thermal printer 1.

From an outward appearance, the thermal printer 1 includes a casing 3having an opening portion 3 a (see FIG. 2), and a paper cover 20 whichis supported on the casing 3 so as to be swingable and opens/closes theopening portion 3 a of the casing 3. Further, inside the thermal printer1, a roll sheet accommodating portion 21 and a printing module 22 areprovided.

The casing 3 is made of plastics such as polycarbonate, or a metalmaterial. A front portion of the casing 3 is formed into substantially arectangular parallelepiped shape having an upper wall 10, whereas a rearportion thereof is formed into a box shape opening upward. On the upperwall 10 of the casing 3, operation portions 14 for performing a varietyof operations of the thermal printer 1 are arranged. As the operationportions 14, a variety of function switches 15 such as a power switchand a FEED switch are arranged, and a variety of indicator lamps 16 arearranged, such as a POWER indicator lamp provided adjacent to thefunction switches 15, for indicating ON/OFF information of the powerswitch, and an ERROR indicator lamp for indicating an error and the likeof the thermal printer 1. Further, between the upper wall 10 and a sidewall 12 of the casing 3, an open button 18 for the paper cover 20 isprovided.

The paper cover 20 is made of plastics such as polycarbonate. The papercover 20 is supported at its rear end on the casing 3 by a hinge shaft(not shown) so as to be swingable, and a front end of the paper cover 20is engageable with the casing 3 by an engagement portion (not shown).Further, through pressing the above-mentioned open button 18 of thecasing 3, the casing 3 and the paper cover 20 are disengaged from eachother, and thus the paper cover 20 can be opened and closed between aclosed position (see FIG. 1) and an open position (see FIG. 2). Further,when the paper cover 20 is at the closed position, between a front endedge of the paper cover 20 and a rear end edge of the upper wall 10 ofthe casing 3, a clearance is formed along a width direction of thethermal paper P1, and the clearance forms a paper outlet 19 (see FIG. 1)through which the printed thermal paper P1 is discharged.

As illustrated in FIG. 2, the roll sheet accommodating portion 21 isformed in the opening portion 3 a at the rear portion of the casing 3.Specifically, the roll sheet accommodating portion 21 includes a guideplate 23 for holding the roll sheet P, and the guide plate 23 and aninner surface of the paper cover 20 hold the roll sheet P so as to coverthe same. The guide plate 23 is a member which is provided inside thecasing 3 and has an arc cross-section. One end of the guide plate 23extends to the rear end side of the above-mentioned paper cover 20, andthe other end thereof extends to a position close to the printing module22. That is, on an inner peripheral surface of the guide plate 23, anouter peripheral surface of the roll sheet P is held in a contact state,and to the printing module 22, the guide plate 23 guides the thermalpaper P1 drawn from the roll sheet P.

FIG. 3 is a perspective view of the printing module.

As illustrated in FIGS. 2 and 3, the printing module 22 includes: a mainbody unit 24 provided at the rear end edge of the upper wall 10 of thecasing 3; a platen unit 25 provided at the front end edge of the papercover 20 and detachably combined with the main body unit 24; and acutting unit 26 for cutting the thermal paper P1 printed by the printingmodule 22.

As illustrated in FIG. 3, the main body unit 24 includes a main bodyframe 31, a head support member 32 supported on the main body frame 31,a thermal head 33 bonded and fixed onto the head support member 32, anda pair of lock arms 35 for rotatably holding a platen roller 34 of theplaten unit 25, which is described below, with respect to the main bodyframe 31.

The main body frame 31 is a plate-like member including a bottom wallportion 31 a extending in a right-left direction, and a pair of sidewall portions 31 b provided so as to extend upward from both endportions of the bottom wall portion 31 a in the right-left direction. Ata rear end edge of the bottom wall portion 31 a, a guide portion 31 cbent downward is formed. The guide portion 31 c guides the thermal paperP1, which is guided from the above-mentioned guide plate 23, to betweenthe thermal head 33 and the platen roller 34 (to a downstream side in aconveying direction).

At an upper end edge of each side wall portion 31 b, a slit 31 d cutdownward is formed. Into the slit, each end portion of the platen roller34 is fitted.

The head support member 32 is a flat-plate-like member having itsright-left direction along a longitudinal direction. The head supportmember 32 is arranged between the side wall portions 31 b, and thethermal head 33 is bonded and fixed onto a rear surface of the headsupport member 32. Further, a lower end side of the head support member32 is supported by a shaft 38 (see FIG. 4) so as to be swingable. Bothaxial end portions of the shaft 38 are fixed to the side wall portions31 b, respectively. With this configuration, the head support member 32swings about the shaft 38 to a front-rear direction. Further, at upperend portions of the head support member 32, stoppers 37 for regulating aswing range of the head support member 32 are formed. The stopper 37extends outward in the right-left direction of the head support member32, and is formed so as to face an inside of a recess 31 e formed in anupper portion of the side wall portion 31 b of the main body frame 31.Further, the stopper 37 moves inside the recess 31 e along with theswing of the head support member 32 and can be brought into contact withboth end surfaces of the recess 31 e. Further, the stopper 37 abutsagainst the end surfaces of the recess 31 e, to thereby regulate furtherswing of the head support member 32.

The thermal head 33 performs printing on the thermal paper P1 conveyedinto the printing module 22, and is bonded and fixed onto the headsupport member 32 and formed into a rectangular shape in plan view(viewed from the front-rear direction). In this case, the thermal head33 is arranged inside the upper wall 10 of the casing 3 so as to beexposed in the opening portion 3 a, and is arranged in a state in whicha longitudinal direction of the thermal head 33 corresponds to the widthdirection of the thermal paper P1. Further, on a head surface 33 a ofthe thermal head 33, a large number of heating elements 41 are arrayedin parallel to the right-left direction and in an aligned pattern. Notethat, the head surface 33 a is a surface opposing to a printing surfaceof the thermal paper P, and the head surface 33 a and an outerperipheral surface of the platen roller 34 sandwich the thermal paper P.The heating elements 41 of the thermal head 33 are controlled so as togenerate heat based on a signal from a control portion (not shown).Through controlling heat generation of the heating elements 41, lettersand figures of various types can be printed on the printing surface ofthe thermal paper P1.

As illustrated in FIGS. 2 and 3, the platen unit 25 is provided at thefront end edge of the paper cover 20, and includes the platen roller 34which is attachable/detachable to/from the main body frame 31 along withclosing/opening of the paper cover 20. The platen roller 34 is providedso that, when the paper cover 20 is at the closed position, theperipheral surface of the platen roller 34 is held in contact with thethermal head 33 in a state of sandwiching the thermal paper P1 drawnfrom the roll sheet P between the thermal head 33 and the platen roller34. Specifically, the platen roller 34 includes a roller shaft 39 (seeFIG. 4) supported onto the paper cover 20 so as to be rotatable, and arubber roller main body 34 a mounted on the roller shaft 39.

At each end portion of the roller shaft 39, a bearing 34 b (see FIG. 2)is mounted. The bearing 34 b is held between the slit 31 d of the sidewall portion 31 b and the lock arm 35 so that the platen roller 34 isheld so as to be rotatable about a center axis and to beattachable/detachable to/from the main body frame 31. Further, a drivengear (not shown) is fixed to one axial end of the platen roller 34, andmeshes with a gear transmission mechanism 42 fixed to the main bodyframe 31 side when the platen roller 34 is held on the pair of side wallportions 31 b. The gear transmission mechanism 42 is connected todriving means 43 such as a motor, and transmits a rotational drivingforce from the driving means 43 to the driven gear. With thisconfiguration, the platen roller 34 rotates in a state of beingsupported on the pair of side wall portions 31 b, and thus can send outthe thermal paper P1. Note that, when the platen roller 34 is separatedfrom the main body unit 24 (slits 31 d and lock arms 35) along with anopening operation of the paper cover 20, combination is released.

In the above-mentioned main body unit 24, in front of the head supportmember 32, a flat-plate-like elastic member support plate 44 extendingsubstantially in parallel to the head support member 32 is arranged.Further, a plurality of (for example, four) elastic members 45 areinterposed between the head support member 32 and the elastic membersupport plate 44 along the right-left direction, and bias the elasticmember support plate 44 and the head support member 32 in directions soas to separate the same from each other. That is, the elastic members 45always press the head support member 32 toward the platen roller 34.

The above-mentioned lock arm 35 is a member integrally extendingrearward from each end portion of the above-mentioned elastic membersupport plate 44 in the right-left direction. The lock arm 35 includesan arm portion 35 a formed on a proximal end side (front end side), anda hook portion 35 b formed on a distal end side (rear end side).

The arm portions 35 a extend rearward from the both end portions of theelastic member support plate 44 so as to interpose the head supportmember 32 therebetween, and are supported so as to be swingable aboutthe above-mentioned shaft 38. Therefore, the elastic member supportplate 44 and the lock arms 35 are swingable about the shaft 38 to thefront-rear direction. Further, at the time of the forward swing (swingto an opposite side of the head support member 32) of theabove-mentioned elastic member support plate 44 and the lock arms 35,the elastic member support plate 44 abuts against the main body frame31, to thereby regulate the further swing of the elastic member supportplate 44 and the lock arms 35.

The hook portion 35 b is provided so as to extend from the distal endside of the arm portion 35 a so as to cover an outer peripheral surfaceof the bearing 34 b of the platen roller 34. In an inner peripheral edgeof the hook portion 35 b, a recess 35 c for supporting the outerperipheral surface of the bearing 34 b of the platen roller 34 isformed. The recess 35 e and the slit 31 d of the side wall portion 31 bhold the bearing 34 b of the platen roller 34.

As described above, the pair of lock arms 35 are formed integrally withthe elastic member support plate 44, and the elastic member supportplate 44 and the head support member 32 are biased by the elasticmembers 45 in opposite directions. Thus, each of the lock arms 35 canhold the platen roller 34 to keep the platen roller 34 rotatable whilethe recess 35 c of the hook portion 35 b and the slit 31 d sandwich thebearing 34 b of the platen roller 34.

As illustrated in FIG. 2, the cutting unit 26 includes: a first cuttingblade 26 a provided on the downstream side relative to the platen roller34 in the conveying direction of the thermal paper P1 and formedintegrally with the front end edge of the paper cover 20; and a secondcutting blade 26 b provided on the downstream side relative to thethermal head 33 and formed integrally with the rear end edge of theupper wall 10 of the casing 3. Further, the thermal paper P1 havingpassed the thermal head 33, that is, the printed thermal paper P1 issent out through the paper outlet 19 formed between the first cuttingblade 26 a and the second cutting blade 26 b, and then cut by beingpulled down in a contact state with the first cutting blade 26 a or thesecond cutting blade 26 b.

(Pressing Force Releasing Mechanism)

FIG. 4 is a sectional view taken along the line A-A of FIG. 3.

Here, as illustrated in FIG. 4, of the above-mentioned elastic members45, an elastic member 45 a, which is provided on one end side (geartransmission mechanism 42 side) in the right-left direction, is providedwith a pressing force releasing mechanism 51 for enabling the elasticmember 45 a to be brought into contact with and separated from the headsupport member 32.

The pressing force releasing mechanism 51 includes a bearing surface 52for supporting the head support member 32 side (rear end side) in anexpansion/contraction direction (front-rear direction) of the elasticmember 45 a, and a lever member 53 connected to the bearing surface 52,for operating the pressing force releasing mechanism 51.

The bearing surface 52 is a C-shaped member opening forward, andincludes a bottom wall portion 55 arranged between the head supportmember 32 and the elastic member 45 a, and side wall portions 56provided upright and forward from both right and left sides of thebottom wall portion 55.

The bottom wall portion 55 is arranged on a front surface of the headsupport member 32, for supporting one end of the elastic member 45 a.Note that, the other end of the elastic member 45 a abuts against theelastic member support plate 44.

The respective side wall portions 56 are formed so as to surround bothsides of the elastic member 45 a in the right-left direction, and a gapis formed between a distal end portion (front end portion) of each ofthe side wall portions 56 and the elastic member support plate 44.

The lever member 53 includes an extending portion 57 extending downwardfrom a lower end portion of the bottom wall portion 55, and an operationportion 58 extending rearward from a lower end portion of the extendingportion 57.

The extending portion 57 extends downward along the front surface of thehead support member 32, and the lower end portion of the extendingportion 57 reaches the bottom wall portion 31 a of the main body frame31.

The operation portion 58 extends rearward over the bottom wall portion31 a of the main body frame 31, and a distal end portion (rear endportion) of the operation portion 58 protrudes to the rear of the bottomwall portion 31 a. Specifically, the rear end portion of the operationportion 58 extends so as to face the inside of the above-mentioned rollsheet accommodating portion 21. Through gripping the operation portion58 through the opening portion 3 a of the casing 3, the pressing forcereleasing mechanism 51 can be operated. That is, through operating theoperation portion 58 along the front-rear direction, the pressing forcereleasing mechanism 51 is movable along the front-rear direction. Notethat, in FIG. 2, for easy understanding of the drawing, the operationportion 58 is exaggeratedly illustrated, but it is preferred that theoperation portion 58 do not interfere with the roll sheet P fed into theroll sheet accommodating portion 21, and be provided at such a positionas to allow a user to grip the operation portion 58 through the openingportion 3 a.

Further, on a lower surface of the operation portion 58, a protrudingportion 59 protruding downward is formed. The protruding portion 59 canbe received in a plurality of positioning holes 61, 62 formed in thebottom wall portion 31 a of the main body frame 31. The positioningholes 61, 62 are formed so as to be aligned and spaced in the front-reardirection at positions overlapping the protruding portion 59 when viewedfrom the front-rear direction. Further, when the protruding portion 59is received in any one of the positioning holes 61, 62, an outerperipheral surface of the protruding portion 59 and an inner peripheralsurface of the one of the positioning holes abut against each other, tothereby regulate movement of the pressing force releasing mechanism 51in the front-rear direction.

In this case, the pressing force releasing mechanism 51 is movablebetween a pressing force imparting position (contact position) (see FIG.4) at which the protruding portion 59 is received in, of the positioningholes 61, 62, the positioning hole 61 formed on the rear side, and apressing force releasing position (separated position) (see FIG. 5) atwhich the protruding portion 59 is received in the positioning hole 62formed on the front side. That is, the above-mentioned protrudingportion 59 and the positioning holes 61, 62 function as positioningportions for positioning the pressing force releasing mechanism 51 atthe pressing force imparting position and the pressing force releasingposition, respectively. In this case, at the pressing force impartingposition, the elastic member 45 a abuts against the head support member32 through intermediation of the bottom wall portion 55, to therebypress the head support member 32 toward the platen roller 34. Meanwhile,at the pressing force releasing position, the elastic member 45 a andthe bottom wall portion 55 are separated from the head support member 32so that the pressing of the head support member 32 by the elastic member45 a is released.

(Way of Actuating Thermal Printer)

Next, a way of actuating the above-mentioned thermal printer 1 isdescribed. Note that, in the following, description is mainly made of afirst roll sheet mode in which printing is performed on the roll sheet Phaving a maximum width (for example, 4-inch width) settable in thethermal printer 1 (hereinafter, referred to as first roll sheet P), asecond roll sheet mode in which printing is performed on a second rollsheet P′ (see FIG. 8) having a smaller width (for example, 3-inch width)than that of the first roll sheet P, and a switching operation betweenthe respective modes. Further, in the following, first, description ismade of a state in which the pressing force releasing mechanism 51 iskept at the pressing force imparting position.

First, as illustrated in FIG. 2, after the open button 18 is pressed toopen the paper cover 20, the first roll sheet P is set. Specifically,the first roll sheet P is set as if being thrown into the roll sheetaccommodating portion 21. In this way, the outer peripheral surface ofthe first roll sheet P is held in a contact state with the innerperipheral surface of the guide plate 23 of the roll sheet accommodatingportion 21. Then, the thermal paper P1 is drawn from the first rollsheet P, and a leading edge of the drawn thermal paper P1 is held incontact with the platen roller 34 and the thermal head 33 therebetween.Thereafter, the paper cover 20 is closed. Thus, setting of the firstroll sheet P is completed.

Then, when the thermal printer 1 is actuated and the platen roller 34 isrotated, the thermal paper P1 is drawn from the first roll sheet P to besent out to the downstream side, that is, to the paper outlet 19 in asandwiched state between the peripheral surface of the platen roller 34and the thermal head 33. At the same time, the thermal head 33, on whichthe large number of heating elements 41 generate heat as appropriate,can clearly print letters and figures of various types on the sent-outthermal paper P1. Thereafter, the thermal paper P1 discharged from thepaper outlet 19 is tilted and pulled toward the cutting unit 26, andthus the thermal paper P1 is cut. As a result, the thermal paper P1rolled in the first roll sheet P can be used as a receipt or the like.

In a case of switching from the above-mentioned first roll sheet mode tothe second roll sheet mode, after the open button 18 is first pressed toopen the paper cover 20, the roll sheet P is taken out of the roll sheetaccommodating portion 21.

Thereafter, the second roll sheet P′ having a smaller width (forexample, 3-inch width) than that of the first roll sheet P is set insidethe roll sheet accommodating portion 21 in a similar way to that of theabove-mentioned first roll sheet mode. At this time, one widthwise endside of the second roll sheet P′ is set so as to align with one sidewall 12 of the casing 3.

By the way, in a case of using the second roll sheet P′ having a smallerwidth than that of the first roll sheet P which has a maximum widthusable in the thermal printer 1, the gap is formed on an outer side ofthe second roll sheet P′ inside the roll sheet accommodating portion 21(between the other widthwise end side of the second roll sheet P′ andthe other side wall 12 of the casing 3). Further, in the gap, thethermal paper P1′ is not present between the thermal head 33 and theplaten roller 34, and thus the thermal head 33 and the platen roller 34are brought into direct contact with each other (contact region R inFIG. 6).

FIGS. 5 and 6 are explanatory diagrams illustrating the switchingoperation from the first roll sheet mode to the second roll sheet mode.FIG. 5 is a sectional view corresponding to FIG. 4, and FIG. 6 is a planview of the casing.

As illustrated in FIGS. 5 and 6, the operation portion 58 is operated todisengage the protruding portion 59 from the positioning hole 61, andthe operation portion 58 is pushed forward. Then, the operation portion58 is moved to a position at which the protruding portion 59 of theoperation portion 58 overlaps the positioning hole 62. When theoperation portion 58 is moved, the pressing force releasing mechanism 51is moved forward, and the elastic member 45 a supported on the bearingsurface 52 contracts. In this way, the elastic member 45 a (bearingsurface 52) is separated from the head support member 32. Further, whenthe protruding portion 59 is received in the positioning hole 62,movement in the front-rear direction of the operation portion 58 isregulated, and the pressing force releasing mechanism 51 is kept at thepressing force releasing position. That is, when the elastic member 45 ais separated from the head support member 32, the pressing of the headsupport member 32 by the elastic member 45 a is released.

With the above-mentioned procedure, the switching operation to thesecond roll sheet mode is finished. Then, printing on the second rollsheet P′ is performed in a similar way to that of the above-mentionedfirst roll sheet mode.

As described above, when the pressing force releasing mechanism 51 movesthe elastic member 45 a from the pressing force imparting position tothe pressing force releasing position, the elastic member 45 a isseparated from the head support member 32, and thus a pressing forceacting from the elastic member 45 a to the head support member 32 can bereleased. That is, it is possible to avoid direct impartation of thepressing force to a portion at which the thermal head 33 and the platenroller 34 are brought into direct contact with each other.

Note that, at the pressing force releasing position, the elastic member45 a imparts a biasing force in a direction so as to separate the bottomwall portion 55 of the bearing surface 52 and the elastic member supportplate 44 from each other. However, the pressing force releasingmechanism 51 is regulated in its movement in the front-rear directionwhen the protruding portion 59 is received in the positioning hole 62,whereas the elastic member support plate 44 is regulated in its swingrange by abutting against the main body frame 31. Thus, a distancebetween the bottom wall portion 55 and the elastic member support plate44 is kept constant.

Further, in a case of switching from the second roll sheet mode to thefirst roll sheet mode, it is only necessary to follow a reverseprocedure to the above-mentioned procedure. That is, the operationportion 58 is operated to disengage the protruding portion 59 from thepositioning hole 62, and the operation portion 58 is pulled rearward.Then, the operation portion 58 is moved to a position at which theprotruding portion 59 of the operation portion 58 overlaps thepositioning hole 61. When the operation portion 58 is moved, thepressing force releasing mechanism 51 is moved rearward, and the elasticmember 45 a supported on the bearing surface 52 expands. In this way,the elastic member 45 a abuts against the head support member 32 throughintermediation of the bearing surface 52. Further, when the protrudingportion 59 is received in the positioning hole 61, movement in thefront-rear direction of the operation portion 58 is regulated, and thepressing force releasing mechanism 51 is kept at the pressing forceimparting position. That is, the elastic member 45 a abuts against thehead support member 32 through intermediation of the bearing surface 52,to thereby always press the head support member 32 toward the platenroller 34.

With the above-mentioned procedure, the switching operation to the firstroll sheet mode is finished.

As described above, in this embodiment, there is adopted a configurationprovided with the pressing force releasing mechanism 51 for separatingthe elastic member 45 a from the thermal head 33 (head support member32) according to the width of the roll sheet P fed into the roll sheetaccommodating portion 21, and for releasing the pressing of the headsupport member 32 by the elastic member 45 a.

With this configuration, in a case of using the second roll sheet P′having a smaller width than that of the first roll sheet P, it ispossible to release the pressing force acting from the elastic member 45a to the head support member 32. Thus, between the thermal head 33 andthe platen roller 34, it is possible to actively reduce contact pressure(platen pressure) between the thermal head 33 and the platen roller 34in the contact region R, and hence it is possible to reduce frictionload between the thermal head 33 and the platen roller 34. Therefore,while reducing damage caused by abrasion between the thermal head 33 andthe platen roller 34, it is possible to handle the plurality of kinds ofroll sheets P, P′ each having a different width in the same apparatus.Further, the reduction of the damage caused by the abrasion enables alonger life of the apparatus.

In addition, when compared to a conventional case in which a pluralityof kinds of platen rollers are separately prepared according to thewidth of the roll sheet P, it is also possible to reduce cost of theapparatus.

Further, in this embodiment, through switching a contact/separated statebetween the elastic member 45 a and the head support member 32 byoperation of the lever member 53, a user himself/herself can easilyperform an operation of releasing the pressing force, which can improveusability. Further, for example, when compared to such a configurationas that requiring detachment of the elastic member 45 a in order torelease the pressing force exerted by the elastic member 45 a, it ispossible to easily perform the operation of releasing the pressingforce.

Further, the bearing surface 52 surrounds the both sides of the elasticmember 45 a in the right-left direction, and hence at the time ofcontraction, movement, and the like of the elastic member 45 a, it ispossible to restrain tilting down of the elastic member 45 a.

In addition, the protruding portion 59 of the operation portion 58, andthe positioning holes 61, 62 (positioning portions) can position thepressing force releasing mechanism 51 at the pressing force impartingposition and the pressing force releasing position, and hence it ispossible to improve reliability of the apparatus.

Note that, the technical scope of the present invention is not limitedto the above-mentioned embodiment, but various modifications can be madewithout departing from the spirit of the present invention.

For example, in this embodiment, description is made of a case of usingthe roll sheet which is rolled so as to have the hollow hole, but a rollsheet obtained by rolling the thermal paper around a core may be used.

Further, in the above-mentioned embodiment, of the elastic members 45,the utmost elastic member 45 a is provided with the pressing forcereleasing mechanism 51, but the present invention is not limitedthereto. An arbitrary one of the elastic members 45 may be provided withthe pressing force releasing mechanism 51.

In addition, in the above-mentioned embodiment, description is made of aconfiguration in which coil springs are used as the elastic members 45,but the present invention is not limited thereto. Plate springs ortorsion bars may be used.

Further, in the above-mentioned embodiment, the operation portion 58 ofthe lever member 53 is extended rearward and can be operated inside theroll sheet accommodating portion 21, but as long as the elastic member45 a can be brought into contact with and separated from the headsupport member 32, design of the configuration of the lever member 53can be modified as appropriate. For example, the operation portion 58may be extended forward.

Another Embodiment

FIG. 7 is a perspective view illustrating a printing module of a thermalprinter according to another embodiment of the present invention.Further, FIG. 8 is a sectional view taken along the line B-B of FIG. 7.FIG. 9 is an explanatory diagram illustrating a switching operation froma first roll sheet mode to a second roll sheet mode, and is a sectionalview corresponding to FIG. 8. Note that, in those figures, the samemembers as those of the above-mentioned embodiment are denoted by thesame reference symbols, and description thereof is omitted.

As illustrated in FIG. 7, similarly to the above-mentioned embodiment,in the main body unit 24 according to this embodiment, a flat-plate-likeelastic member support plate 44A extending substantially in parallel tothe head support member 32 is arranged in front of the head supportmember 32. Between the head support member 32 and the elastic membersupport plate 44A, the plurality of (four, in this case) elastic members45 are interposed along the right-left direction. Further, asillustrated in FIG. 8, of the plurality of elastic members 45, one endof the elastic member 45 a, which is arranged on one end side in theright-left direction (gear transmission mechanism 42 side), passesthrough an elastic member window portion drilled in the elastic membersupport plate 44A, and is supported and fixed on a bottom wall portion55A of a pressing force releasing mechanism 51A provided on a frontsurface side of the elastic member support plate 44A. Meanwhile, theother end of the elastic member 45 a abuts against the head supportmember 32.

The pressing force releasing mechanism 51A includes a lever member 53Afor performing an operation of releasing the pressing force, and theflat-plate-like bottom wall portion 55A formed integrally with the levermember to extend along the front surface of the elastic member supportplate 44A.

The lever member 53A includes an extending portion 57A extendingdownward from a lower end portion of the bottom wall portion 55A, andthe operation portion 58 extending rearward from a lower end portion ofthe extending portion 57A. Similarly to the above-mentioned embodiment,on the lower surface of the operation portion 58, the protruding portion59 protruding downward is formed. The protruding portion 59 can bereceived in the plurality of positioning holes 61, 62 formed in thebottom wall portion 31 a of the main body frame 31.

The pressing force releasing mechanism 51A is movable between a pressingforce imparting position (see FIG. 8) at which the protruding portion 59is received in, of the positioning holes 61, 62, the positioning hole 61formed on the rear side, and a pressing force releasing position (seeFIG. 9) at which the protruding portion 59 is received in thepositioning hole 62 formed on the front side. That is, theabove-mentioned protruding portion 59 and the positioning holes 61, 62function as positioning portions for positioning the pressing forcereleasing mechanism 51A at the pressing force imparting position and thepressing force releasing position, respectively. In this case, at thepressing force imparting position, an elastic force of the elasticmember 45 a is generated between the head support member 32 and thebottom wall portion 55A of the pressing force releasing mechanism 51Asupported and fixed on the main body frame 31 through the protrudingportion 59 and the positioning hole 61, and the elastic member 45 apresses the head support member 32 toward the platen roller 34.Meanwhile, at the pressing force releasing position, when the bottomwall portion 55A of the pressing force releasing mechanism 51A movesforward (to the right side of FIG. 9), a stroke of the elastic member 45a is increased so that the pressing force acting on the head supportmember 32 is reduced.

Note that, the switching operation between the first roll sheet mode andthe second roll sheet mode (that is, the switching operation between thepressing force imparting position and the pressing force releasingposition) is performed in a similar way to that of the above-mentionedembodiment, and hence description thereof is omitted here.

As described above, in this embodiment, according to the width of theroll sheet P fed into the roll sheet accommodating portion 21, thestroke of the elastic member 45 a biasing the head support member 32toward the platen roller 34 is increased so that the pressing force isreduced. With this configuration, it is possible to obtain the samefunctions and effects as those of the above-mentioned embodiment.

What is claimed is:
 1. A printer for performing printing on a pluralityof kinds of roll sheets each having a different width, the printercomprising: a thermal head comprising a large number of heating elementsarranged along a width direction of a thermal paper that is drawn fromone of the plurality of kinds of roll sheets; a platen roller arrangedopposite to the thermal head and mounted to undergo rotation for sendingout the thermal paper in a state of sandwiching the thermal paperbetween the thermal head and the platen roller; and a plurality ofelastic members arrayed along the width direction and provided on anopposite side of the platen roller with respect to the thermal head forpressing the thermal head toward the platen roller; wherein only one ofthe plurality of elastic members is provided with a pressing forcereleasing mechanism for separating the one elastic member from thethermal head according to a width of the one of the plurality of kindsof roll sheets from which the thermal paper is drawn and for releasingpressing of the thermal head by the one elastic member.
 2. A printeraccording to claim 1, wherein the pressing force releasing mechanismcomprises a lever member for moving the one elastic member and forenabling the one elastic member to be brought into contact with andseparated from the thermal head.
 3. A printer according to claim 2,wherein the pressing force releasing mechanism comprises a positioningportion for keeping the one elastic member at a contact position, atwhich the one elastic member is brought into contact with the thermalhead, and at a separated position, at which the one elastic member isseparated from the thermal head.
 4. A printer according to claim 1,wherein the pressing force releasing mechanism comprises a positioningportion for keeping the one elastic member at a contact position, atwhich the one elastic member is brought into contact with the thermalhead, and at a separated position, at which the one elastic member isseparated from the thermal head.
 5. A printer according to claim 1,wherein the one elastic member is arranged at a position correspondingto one end side in the width direction of the thermal paper.
 6. Aprinter according to claim 1, further comprising a head support memberfor supporting the thermal head; and wherein the pressing forcereleasing mechanism comprises a bearing surface for supporting the headsupport member, the bearing surface having a wall portion arrangedbetween the head support member and the one elastic member.
 7. A printeraccording to claim 6, further comprising an elastic member support platefor supporting the plurality of elastic members; and wherein one end ofthe one elastic member is supported by and abuts the wall portion of thebearing surface and the other end of the one elastic member is supportedby and abuts the elastic member support plate.
 8. A printer according toclaim 6, wherein the pressing force releasing mechanism furthercomprises a lever member connected to the bearing surface for operatingthe pressing force releasing mechanism, the lever member having anextending portion extending downward from a lower end portion of thewall portion and having an operation portion extending rearward from thelower end of the extending portion for operation of the pressing forcereleasing mechanism through gripping of the operation portion.
 9. Aprinter for performing printing on a plurality of kinds of roll sheetseach having a different width, the printer comprising: a thermal headcomprising a large number of heating elements arranged along a widthdirection of a thermal paper that is drawn from one of the plurality ofkinds of roll sheets; a platen roller arranged opposite to the thermalhead and mounted to undergo rotation for sending out the thermal paperin a state of sandwiching the thermal paper between the thermal head andthe platen roller; and a plurality of elastic members arrayed along thewidth direction and provided on an opposite side of the platen rollerwith respect to the thermal head for pressing the thermal head towardthe platen roller; wherein only one of the plurality of elastic membersis provided with a pressing force releasing mechanism for moving the oneelastic member so as to increase a stroke of the one elastic memberaccording to a width of the one of the plurality of kinds of roll sheetsfrom which the thermal paper is drawn and for reducing pressing of thethermal head by the one elastic member.
 10. A printer according to claim9, wherein the pressing force releasing mechanism comprises a levermember for moving the one elastic member so as to reduce a pressingforce acting on the thermal head.
 11. A printer according to claim 10,wherein the pressing force releasing mechanism comprises a positioningportion for keeping the one elastic member at a pressing force impartingposition, at which the at one elastic member generates an elastic forcebiasing the thermal head, and at a pressing force releasing position, atwhich the elastic force is reduced by increasing the stroke of the oneelastic member.
 12. A printer according to claim 9, wherein the pressingforce releasing mechanism comprises a positioning portion for keepingthe one elastic member at a pressing force imparting position, at whichthe one elastic member generates an elastic force biasing the thermalhead, and at a pressing force releasing position, at which the elasticforce is reduced by increasing the stroke of the one elastic member. 13.A printer according to claim 9, wherein the one elastic member isarranged at a position corresponding to one end side in the widthdirection of the thermal paper.
 14. A printer according to claim 9,further comprising a head support member for supporting the thermalhead; and wherein the pressing force releasing mechanism comprises abearing surface for supporting the head support member, the bearingsurface having a wall portion arranged between the head support memberand the one elastic member.
 15. A printer according to claim 14, furthercomprising an elastic member support plate for supporting the pluralityof elastic members; and wherein one end of the one elastic member issupported by and abuts the wall portion of the bearing surface and theother end of the one elastic member is supported by and abuts theelastic member support plate.
 16. A printer according to claim 14,wherein the pressing force releasing mechanism further comprises a levermember connected to the bearing surface for operating the pressing forcereleasing mechanism, the lever member having an extending portionextending downward from a lower end portion of the wall portion andhaving an operation portion extending rearward from the lower end of theextending portion for operation of the pressing force releasingmechanism through gripping of the operation portion.
 17. A printer forperforming printing on a plurality of kinds of roll sheets of thermalpaper each having a different width, the printer comprising: a thermalhead; a platen roller arranged opposite to the thermal head and mountedto undergo rotation for feeding the thermal paper in a state in whichthe thermal paper is interposed between the thermal head and the platenroller; and a plurality of elastic members provided on an opposite sideof the platen roller with respect to the thermal head for pressing thethermal head toward the platen roller, one of the plurality of elasticmembers being arranged at a position corresponding to one end side inthe width direction of the thermal paper, and only the one elasticmember being provided with a pressing force releasing mechanism forreleasing pressing of the thermal head by the one elastic member.
 18. Aprinter according to claim 17, further comprising a head support memberfor supporting the thermal head; and wherein the pressing forcereleasing mechanism comprises a bearing surface for supporting the headsupport member, the bearing surface having a wall portion arrangedbetween the head support member and the one elastic member.
 19. Aprinter according to claim 18; further comprising an elastic membersupport plate for supporting the plurality of elastic members; andwherein one end of the one elastic member is supported by and abuts thewall portion of the bearing surface and the other end of the one elasticmember is supported by and abuts the elastic member support plate.
 20. Aprinter according to claim 18, wherein the pressing force releasingmechanism further comprises a lever member connected to the bearingsurface for operating the pressing force releasing mechanism, the levermember having an extending portion extending downward from a lower endportion of the wall portion and having an operation portion extendingrearward from the lower end of the extending portion for operation ofthe pressing force releasing mechanism through gripping of the operationportion.